Kiosk is way to go....how odd and sad that in some ways, the impersonal automation can trump the "customer service" experience with the AA employees...

Don't wait for AA to contact you...Take some of the extra time you have at MIA airport and contact them. Email AA Customer Relations and ask for clarification on the policy for same day standby for Plat. Consider including your impressions of the agent and the supervisor and their attitudes and degree of engagement with your simple request. There are many AA employees who have the world view that they are "doing you a favor" when you have purchased a ticket and have any request other than "shut up and get on the plane".

What is really stupid about the situation is that one of the most perishable commercial commodities is an airline seat. Once the aircraft door closes empty seats are ZERO revenue. It is in AA's interest to get you on the earlier flight. The seat you vacate on the later flight could be sold, needed to support IROPs, and so on...

Do you think AGENT wanted $50 cash? IIRC, recently there was an article in Miami Herald about a criminal sting at MIA with AA with employees pocketing cash for pax excess baggage or something....